Prairie Pothole Region 

The PPR is a region of millions of small depressional wetlands and lakes covering 750,000 km² 

That would make the Prairie Pothole Region the 36th largest country in the world (if it were a country)

The Prairie Pothole Region (PPR) of North America, which spans an area of the northern Great Plains occupying about 750,000 km², contains millions of small depressional wetlands and lakes (the prairie potholes). These features were formed during retreat of glaciers, which left behind a blanket of clay, silt, and sand. Depressions in the landscape filled with water, forming the potholes. These lakes and wetlands and recharged by rain or overland flow of water, and they are connected hydrologically through groundwater.

Wetlands in the upland portion of these small basins tend to contain water only seasonally and water flows from the upland potholes to pothole wetlands at lower elevations through local depression-focused groundwater flow. These lower elevation wetlands tend to contain water year round but may dry out during periods of drought. The upland wetlands have chemistry similar to rainwater, and because the groundwater flows through and dissolves minerals, the discharge wetlands contain high concentrations of ions. The chemistry of wetlands separated by only hundreds of meters can vary drastically. 

In the Upper Midwest/Northern Great Plains, prairie potholes are integral components of the regional hydrology, critical waterways for bird migration, and are important ecosystems. Over half of all North American waterfowl breed in the PPR, and hunting and bird watching are major attractions.

These wetlands are biogeochemical ‘hotspots’, where there is rapid turnover of carbon and nutrients. The release of greenhouse gases, including carbon dioxide and methane, from the wetlands mean that how this process respond to changing climate will be critical to understanding future climate scenarios.  The PPR is also one of the major agricultural areas in the U.S., and the biogeochemical activity in the wetlands processes pollutants, and thus these features serve as filters for agricultural runoff. 

The prairie potholes face multiple threats. For many years, land owners and managers would drain and/or fill wetland to attempt to make more land for crops or grazing. Chemical pollution (nutients and pesticides) have the potential to disrupt the normal ecological functions bay causing algae to grow or impacting the native plant and animal species. Climate change will also impact the wetlands. Warmer temperature may alter the biogeochemical processes and the plants and animals that live in the wetlands. If,  as climate warms, the wetlands may release more greenhouse gases, suchas CO₂ and CH₄, this would further contribute to climate change, exacerbating the problem.

Wildlife abounds in the prairie potholes. Bird species (18 waterfowl, 96 songbirds, 36 waterbirds, 17 raptors, and 5 upland game birds) are particularly abundant, but there are also various reptiles and invertebrates in the wetlands. The pothole region is also home to native prairies (tall grass, eastern mixed grass, mixed grass). Although much has been converted to agriculture, some original tracts of these grasslands remain. 

Economic Value

The PPR plays an important role in agriculture, whereby farmed land comprises approximately 74% of the land area in contrast to 47% nationwide (Sweikert, 2017). As such the PPR is of critical economic value to the nation, and grasslands are now being converted to cropland at an annual rate of 1-5% (Sweikert, 2017). Besides their agricultural value, the PPR provides significant ecosystem services to the region that include carbon sequestration, water retention, and groundwater recharge, critical waterfowl habitats, and outdoor recreation. The conversion of wetlands to croplands, however, has resulted in a significant degradation of these other ecosystem services that the PPR provides. This has resulted in the loss of over half the wetlands in the PPR since the advent of agriculture in the region. (Voldseth et al., 2007).  As such development of this region will need to consider the benefits of preserving and even expanding ecosystem services while considering the expansion of croplands. 

Recreational Value

The region is well known for bird watching and bird hunting opportunities. 

Cultural Value

Native Americans have been in the Prairie Pothole regions since the last Ice Age and are comprised of a rich diversity of cultures e.g., Apsaalooke, Sioux, Mandan, Blackfeet, etc. They possessed a reverence for the land and water resources of the region that changed with the arrival of Europeans, who converted 15 million hectares of prairies to farmland. This agriculture-based economy is complemented by recreational based activities, especially waterfowl hunting (Ducks Unlimited refers to the potholes as “duck factories”) and birdwatching.  These two activities are especially given the location of the PPR in the North American Central Flyway, which offers essential habitats for migratory birds.   

Research

Research has been ongoing in the prairie pothole region for more than five decades and cover a diversity of topics ranging from wildlife biology to environmental biogeochemistry and hydrology.  The prairie ecosystem and its associated wetlands and potholes are particularly sensitive to the combined effects of climate and land use changes and understanding the interplay between these two processes overlain by anthropogenic activity (particularly agriculture) is the focus of much of the ongoing research in the PPR.  Studying the combined effects of a changing climate and alterations to the landscape is needed to assess the resilience of the PPR given the ecosystem services that the prairie and its wetlands have to offer.   These services are highly diverse and critically important to the health of the prairie biome and range from serving as waterfowl habitats to the attenuation of pesticides used in agriculture.  Research conducted in the PPR involves a consortium of academic institutions, government agencies, and nongovernment organizations.  While the topics vary widely, they are commonly linked to studying the effects of anthropogenic activity in the PPR from global to local scales.

Water

The hydrology of the PPR is unique in that both temporary and perennial wetlands are connected by groundwater as opposed to streams.  As such the water chemistry of each wetland varies from upland wetlands (recharge) to those further downgradient (flow-through and discharge).  The water chemistry of recharge wetlands resemble rainwater and is low in ions while discharge wetlands are almost brackish and high in sulfur species.  This phenomenon is caused by  It is these differences that give each pothole a unique biogeochemical profile and microbiome.  Finally, the influence of climate change will determine how these wetlands (and their function) will exist in the future as the North American continent experiences more extreme precipitation and drought events.

Science

 The USGS Northern Prairie Wildlife Research Center studies the native and invasive species in the region and their stressors. They also focus on mangagment and restoration of the prairies, wildlife diseases, and how climate change and land use affect the prairie potholes. A National Ecological Observatory Network (NEON) site, the Dakota Coteau Field School,  funded by the National Science Foundation is part of a group of long term observatories that collect data to understand how ecosystems are changing.